| Official Name: | Kosacha |
| Subdivision Type1: | Province (Oblast) |
| Blank Info Sec1: | PK |
| Blank Name Sec1: | License plate |
| Elevation M: | 822 |
| Established Date: | 1573 |
| Established Title: | First mentioned |
| Timezone1 Dst: | EEST |
| Utc Offset Dst: | +3 |
| Utc Offset: | +2 |
| Timezone1: | EET |
| Subdivision Type2: | Municipality (Obshtina) |
| Subdivision Type: | Country |
| Native Name: | Косача |
| Subdivision Name1: | Pernik |
| Settlement Type: | Village |
| Pushpin Map Caption: | Location of Kosacha |
| Pushpin Map: | Bulgaria |
| Postal Code Type: | Postal Code |
| Postal Code: | 2448 |
| Population Total: | 148 |
| Population As Of: | 2020 |
| Area Land Km2: | 13,344 |
| Coordinates: | 42.5667°N 22.85°W |
| Subdivision Name2: | Kovachevtsi |
Kosacha (Bulgarian: Косача, also transliterated Kosača) is a village in western Bulgaria. Its located in Oblast Pernik, Obshtina Kovachevci.
The village of Kosacha is located in a mountainous region, 16 km southwest of Pernik and 41 km southwest of Sofia.
The village is a conglomeration of neighborhoods scattered over hills and valleys. The neighborhoods are Tyutyundzhiyska, Polyana, Domishlyarska - there is the house of Georgi Parvanov's mother, Evreyska (Jewish), Velichkova - there is his father's house, Eleninska / grandmother Elena hid Levski in the church, wife of grandfather Pene - a merchant in Constantinople. Picked up by a priest from the village of Ruzhdavitsa /, Bradarska mahala, Kyurkchiyska mahala / there are remains of a fortress /, Gruyova mahala, Stoykovi, Todorovi, Kompirovi, Mialovi / Mihailovi /, Gypsy / by nickname /, Kovachevska mahala. The road distance from Tyutyundzhiya to Arbanashki rid is more than 6 km.
The village was first mentioned in the Ottoman archives in 1573.
The ancient town of Buieridava was located near the village and the Lobosh dam (Pchelina). It was founded approx. 5th century BC from the Thracian tribe Ilei.
The name derives from the Bulgarian word Kosach, which means Mower.
There is an alphabet (Cyrillic) containing a list notable Kosachi (Mowers)